A pro-Russian militant wearing a cagoule guards a barricade in front of the Donetsk regional administration building on Tuesday. (Alexander Khudoteply / AFP via Getty Images)

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WASHINGTON — Secretary of State John Kerry on Tuesday threatened Russia with tougher economic sanctions if it fails to back down from its chaotic involvement in Ukraine.

"What we see from Russia is an illegal and illegitimate effort to destabilize a sovereign state and create a contrived crisis with paid operatives across an international boundary," Kerry told the Senate Foreign Relations Committee.

Ukrainian officials said security forces drove pro-Russian protesters out of the regional government headquarters in Kharkiv and arrested about 70 of them, but demonstrators continue occupying the Donetsk regional administration in the nearby region. The protests come a month after Russia annexed the Crimea peninsula, a move the West has not recognized.

Kerry called the demonstrations a "contrived pretext for military intervention just as we saw in Crimea."

President Barack Obama and Congress have imposed sanctions on Russia in response to the annexation, and Kerry signaled the additional penalties on Russian energy, banking and mining could be imposed if Moscow fails to honor a sovereign Ukraine.

Kerry said the U.S. and European allies were united and willing to impose tough new sanctions.

Kerry said he would meet next week in Europe with Russia Foreign Minister Sergey Lavrov and Ukrainian officials. He said Russia has a choice and can work with the international community.

"We have made it clear that Russia needs to take concrete steps to disavow separatist actions in Eastern Ukraine, pull back its forces outside the country — which they say they have begun to do with the movement of one battalion — and demonstrate that they are prepared to come to these discussions to do what is necessary to de-escalate," Kerry said.